GERBERA JAMESONII CULTIVATION WITH DIFFERENT INERT SUBSTRATES

The experiment was particularly aimed at testing the possible influence of the substrates both on the total yield and on the commercial stem quality obtained in the different periods.

The experiment was carried out in an iron and glasshouse with the air heating set at 11 °C, utilizing the cultivars Solara and Mirage, respectively with golden-yellow and orange petals. Micropropagated plantlets transplanted in rock wool cubes were used. The substrates confronted were: pearlite, marc, rock wool, and a synthesis polymer commonly known by the name "idrosorb". The substrates were contained in 22 litre white polyethylene "bags" filled up to three quarters. The transplant was carried out on 30 July 1991 and three plants were placed in each bag, to obtain a plant density of 6.25 plants per square metre.

A complete fertilizer solution of the Cole-Lesaint type with 12.8 me of nitrogen per litre was used.

The solution was distributed by an electronic central system. The volumes were calculated according to the total radiation received.

Production started on 19th September 1991. The number, commercial quality and fresh weight of the cut flowers were recorded between 19th September 1991 and 31 July 1992.

The results have pointed out statistically significative differences in the productions obtained in the different substrates. These differences were less appreciable in autumn and winter, while they were more marked in the spring-summer period.

Mean commercial yields for the two varieties in the considered period were 219. 195, 194 and 171 cut flowers per square metre on pearlite, marc, rock wool and "idrosorb" respectively. The substrates had a significative effect also on the percentage distribution of the stems in the two considered commercial classes. Moreover a positive interaction was found between variety and substrate in relation to the quality of the yields.

The production response obtained for the two varieties grown in marc was particularly interesting for the low unit cost of this substrate and its great availability in Mediterranean areas.